Biodegradable Bag

ABSTRACT

The present invention provides a bag made of a non-woven biodegradable material comprising a body portion having at least one side wall and a bottom joined together to define a storage space therebetween and an opening at the top of the body portion, wherein the bag is biodegradable and non-toxic to the environment

FIELD OF THE INVENTION

The present invention relates generally to disposable biodegradableproducts. In particular, but not exclusively, the present inventionrelates to a non-woven biodegradable bag.

BACKGROUND TO THE INVENTION

Biodegradable and compostable bags are made of polymers that degrade, ordecompose, when exposed to microorganisms in the presence of air, waterand/or sunlight. Biodegradable and compostable bags in the marketplaceare typically made from resins containing polyethylene, polyester andtheir blends with starches and/or heavy metals such as cadmium, lead andberyllium.

Whilst current biodegradable and compostable bags provide a solutionless harmful to the environment, current biodegradable and regulardisposable plastic bags require a similar amount of energy, naturalresources and costs to produce. Also mixing of biodegradable andcompostable bags in recycling systems with conventional plastic bagscreates a strong problem and can render entire batches of recyclableplastic useless.

There is a perception that bag littering could easily increase as peoplestart to believe that biodegradable and compostable bags are lessharmful to the environment and will disappear quickly, when it realityit takes at least several months for most current biodegradable andcompostable bags to breakdown. Further, the breakdown of starch-basedfilms in water consumes oxygen, resulting in oxygen depletion thatcontributes to algae blooms and the death of marine life. Consequently,water, soil, and/or crop contamination could result from the use ofcompost with chemical residues and metabolites from biodegradable bags.

In this specification, the terms ‘comprises’, ‘comprising’ or similarterms are intended to mean a non-exclusive inclusion, such that anon-woven biodegradable bag that comprises a list of elements does notinclude those elements solely, but may well include other elements notlisted.

OBJECT OF THE INVENTION

It is a preferred object of the present invention to provide a non-wovenbiodegradable and compostable bag which can be used as a recyclablecarry bag, that addresses or at least ameliorates one or more of theaforementioned problems of the prior art.

It is a preferred object of the present invention to provide a non-wovenbiodegradable and compostable bag which is biodegradable and provides acost-effective compostable alternative to existing products in themarketplace.

SUMMARY OF THE INVENTION

Generally, embodiments of the present invention relate to a non-wovenbiodegradable bag and method of manufacturing same.

According to one aspect, although not necessarily the broadest or onlyaspect, embodiments of the present invention reside, in a bag made of anon-woven biodegradable polylactide based material, wherein the materialcontains polylactic acid, polyethylene glycol and a chain extender suchthat the bag is biodegradable and degraded products are non-toxic to theenvironment.

Preferably, the bag is a shopping bag.

Suitably, the bag further comprises a pair of handles, wherein the pairof handles are attached to a top of the body portion at their ends.

Preferably, the bag further comprises at least one strap member.

Suitably, the strap member is attached at or near the top of bodyportion and extends across the opening of the body portion of the bag.

Suitably, the strap member is permanently secured at a first end to afirst side of the body portion, the body portion having a fasteningmember to releasably secure a second end of the strap member to a secondopposing side of the body portion.

Suitably, the bag further comprises a pair of apertures provided at ornear the top of the body portion for receiving a prong membertherethrough to hold the bag in an open state for example, at thecheckout.

Preferably, the biodegradable non-woven material comprises one or moreof the following polymers: polylactic acid, polyethylene glycol, chainextender Joncryl—ADR 4370.

Preferably, the material composition of the biodegradable non-wovenmaterial is 91-94% polylactic add, 5-8% polyethylene glycol and 1% chainextender.

Preferably, the biodegradable non-woven material has a weight-averagemolecular weight ratio above 160000, a dispersion coefficient ≦1.5, amelt index between 20-30 and a water content ≦0.9%.

According to another aspect, although again not necessarily the broadestor only aspect, embodiments of the present invention reside in a methodof manufacturing a non-woven biodegradable bag comprising the followingsteps:

preparing a biodegradable non-woven material mixture;

drying the material to remove residual moisture;

extruding a Polylactide (PLA) slicing;

heat melting the extruded PLA slicing;

purifying the melted PLA material;

spinning the material;

cooling and retracting the material;

needling the material onto a roll; and

forming the bag from the roll of material.

Preferably, the material is vacuum dried at 80-90° C. such that themoisture content of the PLA slicing is less than 200 PPM.

Preferably, the extruded PLA slicing is heat melted using a heat screwextruder.

Preferably, the melted PLA material is filtered prior to the spinningprocess using a high viscosity fondant proportional pump to squeeze outthe impurities by rotation.

Further features of the present invention will become apparent from thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be readily understood and put intopractical effect, reference will now be made to embodiments of thepresent invention with reference to the accompanying drawings, whereinlike reference numbers refer to identical elements. The drawings areprovided by way of example only, wherein:

FIG. 1 is a perspective view of a non-woven biodegradable bag accordingto an embodiment of the present invention;

FIG. 2 is a perspective view of the non-woven biodegradable bag of FIG.1 comprising a strap member according to an embodiment of the presentinvention;

FIG. 3 is a perspective view of an alternative embodiment of thenon-woven biodegradable bag of FIG. 1 comprising at least one aperture;and

FIG. 4 is a flow diagram of the method for producing the non-woven bagbiodegradable bag of FIGS. 1-3 according to embodiments of the presentinvention.

Skilled addressees will appreciate that elements in the drawings areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the relative dimensions of some of theelements in the drawings may be distorted to help improve understandingof embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described with reference toa non-woven biodegradable and compostable bag for use as a recyclableand disposable carry bag. However, it should be appreciated thatembodiments of the present invention can be used to provide a non-wovenbiodegradable product which can be used for any other suitableapplications such as secondary food packaging including take-away foodpackaging or the like. It will be appreciated that variations may needto be made as required.

Referring to FIG. 1, the non-woven biodegradable bag 100 is provided inaccordance with embodiments of the present invention. According to someembodiments of the invention, the non-woven biodegradable bag ismanufactured from a completely biodegradable Polylactide (PLA) non-wovenmaterial. PLA is a high crystalloid and linear polymer which satisfiesthe two primary conditions for wiredrawing to make a non-woven material.PLA or its derivatives, such as L and D type or copolymers, is adegradable polymer having good mechanical properties, the degradableproducts are natural materials, the degradation time can be varied, theraw material comes from renewable sources such as beet sugar or whey andit can be incinerated without major difficulty or drawbacks. Theproperties of the PLA non-woven material of the present inventioninclude being a good hydrophilic, soil resistance, deodorisation,fire-resistance and microbial decomposability, all of which provideunique characteristics to the present invention. These properties alsomake this material the best candidate for a material for use indisposable environmental production. The properties of polymers derivedfrom polylactides vary depending on the type of polymer (L or D type),on the residual amount of monomer (lactide) and, in the case of DLcopolymers, on the ratio of D units to L units.

Referring to FIG. 1, the non-woven biodegradable bag 100 comprises abody portion 110 for carrying items therein. According to someembodiments, the body portion 110 comprises at least one side wall 113and a bottom 114. When joined together, the side wall(s) 113 and bottom114 define a storage space therebetween with an opening 120 at a top ofthe body portion 110. A preferred box-like shape for the non-wovenbiodegradable bag 100 is illustrated in FIG. 1 comprising four sidewalls 113.

The bag 100 is preferably sized to hold the contents of a conventionalgrocery shopping bag. However, as will be apparent to those skilled inthe art, the body portion 110 can have various shapes and sizesdepending on the intended use of the end product. It is envisaged thatone skilled in the art can design any number of body configurationsaccording to the invention bearing in mind the limitations andadvantages of the materials used and the intended use. For example, alarger body portion 110 can be used if the beg is intended for use as abeach bag or gym bag.

According to some embodiments, a pair of handles 200 is provided forcarrying the bag 100. Preferably, the handles 200 are attached by theirends 112 to the top of the body portion 110 of the bag 100 via stitchingor any other suitable means enabling permanent attachment. In furtherembodiments of the present invention, the handles 200 can have anadjustable length to be shorter or longer as is required.

According to some embodiments, the bag 100 has at least one printablearea 111 for displaying a company logo, advertising or any othersuitable information. Preferably, the material of the bag 100 is suchthat information can be printed directly onto the bag material using asuitable biodegradable ink and standard printing machine to minimiseproduction costs.

Referring now to FIG. 2, the non-woven biodegradable bag 100 can haveone or more optional features attached to the body portion 110.According to some embodiments, the bag 100 further comprises at leastone strap member 300 which acts as a tension member for the bag 100.According to some embodiments, the strap member 300 is attached at ornear the top of body portion 110 and extends across the opening 120 ofthe bag 100. In FIG. 2, one strap member 300 is shown. However, infurther embodiments, more strap members 300 can be included to provideadditional support for the bag 100.

The strap member 300 is preferably permanently secured at a first end301 to a first side of the body portion 110. The body portion 110 has afastening member 310 provided on a second opposing side of the bodyportion 110 to releasably secure a second end 302 of the strap member300 to the body portion 110. In an alternative embodiment, both ends301, 302 of the strap member 300 can be releasably secured to the bodyportion 110. Preferably, the fastening member 310 for releasablysecuring the strap member 300 to the body portion is a snap fastener butany other suitable fastening device can also be used. For example, hookand loop type fasteners can be used.

According to an alternative embodiment illustrated in FIG. 3, thenon-woven biodegradable bag 100 comprises a pair of apertures 120provided at or near the top of the body portion 110. Preferably, theapertures 120 are provided on the first and second opposing sides of thebody portion 110 of the bag 100. The apertures 120 are adapted toreceive a prong member or the like provided at a shopping counter forholding the bag 100 in an open state. As illustrated in FIG. 3, in analternative embodiment of the non-woven biodegradable bag, the pair ofhandles 200 can be omitted.

In further embodiments of invention, it is envisaged that the non-wovenbiodegradable bag can have additional features to provide addedfunctionality for the bag and/or suit other applications. The non-wovenbiodegradable bag 100 can have provided one or more pockets (notillustrated). These pockets can be sized to hold or secure specificitems such as, for example, a cell phone, wallet, keys, or glasses orthe like. The interior of the body portion 110 can also have providedone or more dividers for enabling the separation of items and organisingpacking of items within the bag 100.

Referring now to FIG. 4, a schematic diagram of a method 400 forproducing the non-woven biodegradable product is illustrated. The mainequipment required for the production of PLA non-woven material includesa plastic particle dry system, a spinning unit, a drafting lay-downsystem, a needling unit and a roil unit. According to some embodiments,the material composition of the non-woven PLA material is as follows:

1. PLA—91˜44%

Technical requirement

-   -   Weight-average molecular weight ratio is between 150000 to        220000    -   Melting point 160˜170° C.    -   Crystallization temperature 50˜80° C.    -   Moisture content 5500 ppm

2. Polyethylene Glycol (PEG)—5˜8%

Technical requirement

-   -   Weight-average molecular weight ratio is between 5000 to 20000    -   Melting point 50˜65° C.    -   dynamic viscosity 30˜35 mm²/s,    -   pH value: 4˜7    -   The PEG used PEG4000—molecular formula is HO(CH2CH2O)nH

-   -   It mainly provides a toughening reagent when used in molten        extrusion wiredrawing while still allowing adjustment of the        melt molten index to facilitate easy drawing.

3. Chain extender ADR4370 1%

-   -   The Joncryl—ADR4370 maximises melt viscosity through branching        where high melt strength is needed for steady parisons,        non-sagging profiles, and dosed-cell, low-density foams. Its        every molecule has eight epoxy groups which can react with the        hydroxyl group in the polylactic acid molecules, forming a chain        structure. The main aim of We using the chain extender is to        increase the products intensity, and partial repair the cut        molecular chain during the manufacture process when the        molecular chain is cut by the twin-screw extruder.

Material Drying Process

The PLA grade required for the preparation of the present invention isfibre-grade PLA material having a weight-average molecular weight above160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and awater content ≦0.5%. Polylactide physical properties, especially thetensile strength parameters will increase as the molecular weight isincreased. By using different molecular weights, the PLA fiber can alsohave different tensile strength. For example, using a molecular weightbelow 150,000 polylactic acid to produce polylactic acid fiber, thetensile strength is low and can not reach strength requirements for thenon-woven material and bag. If the molecular weight were higher than220,000 polylactic add, although its fibre strength is high, because ofthe high viscosity of molten body of the PLA material, shear stress islarger and hard to withstand for the production equipment. For example,for 150,000 molecular weight of polylactide, its production of fibretensile strength is 1.1 Mpa, but for 220,000 molecular weight ofpolylactide, its production of fibre tensile strength can reach 2.6 Mpa.

The moisture content is the most important of the above parametersbecause PLA is hydrolysable at high melt temperatures causing themolecular chain to rupture and the molecular weight to decrease. Thiskind of circumstance can make the output of the strength of fiber lowerand very easy to be broken. Thus, it is necessary to let the rawmaterial dry fully. In order to avoid this issue, the material undergoesa further drying process to desiccate the PLA polymer and removeresidual moisture to reduce the moisture content to a level wherehydrolysis is insignificant. Preferably, the moisture content of a PLAslicing should be less than 200 PPM and is achieved by vacuum drying at80-90° C. The drying process can be carried out utilising a rake vacuumdrying system or the like.

According to experience value, a PLA raw material used for producingfilm must be dried to a moisture content of below 200 PP and a PLA rawmaterial used for producing fibre must dried to moisture content of 30PPM below.

Melt Extrusion Process

In this process, the polymer is melted and extruded by means of a heatedsingle-screw or twin-screw extruder and then conveyed to a spinningpump. If a double screw extruder is chosen the length-diameter ratio ofthe screws should be considered. The specification of the extruderdiameter can be 135 mm. Care must be taken while kneading during theextrusion process so as not to destroy the PLA polymer chain in theprocessing cycle and then influence the stretch of the tactile fibre andbreak the fibre or decline the single fibre tenacity.

Using custom made extruders for this process, for extruderspecifications the diameter is 135 mm, length-diameter ratio is 1:25,dividing into six district for heating and cooling zone before firstdistrict; the cooling district and the first district is the area forfeeding section, second and third district is compressed section, forthdistrict and fifth district is measurement section, sixth district ismixing section.

After PLA resin is melted by the screw extruder, the PLA fondantimpurities must be removed which is achieved by introduction of a filterfilm head with a filter level of 20 μm. After the PLA fondant is passedthrough the filter film it goes through a high viscosity fondantproportional pump to squeeze out the impurities by rotation. Theproportional pump frequency is controlled according to the output andproduct features required. The proportional pump with temperaturecontrol provides uniform flow of the molten polymer.

On leaving the pump, the stream of molten polymer is conveyed throughthe filter to the spinneret, which contains a series of small holes (0.2to 2.0 mm in diameter), usually of the order of several thousand holes.The polymer is spun through the spinneret and conveyed to the coolingand drawings sections. The specification selected in this instance forthe non-woven spinneret plate bore diameter is 0.25-0.35 mm. This isbased on a preferred narrow processing window for the PLA material andthe allowed processing temperature range. According to some embodiments,the diameter of plate bore is according to the requirement of silkflock. In this case, every flock of silk is 90˜96 roots, so the thediameter of plate bore is 10 mm. When spinning, the lowest melttemperature for the melting point is around 170° C., otherwise materialcannot melt and also cannot be spun. The highest temperature is around210° C., if higher, poly lactic add will very easily decompose. Thelowest draw ratio is 80.

As the temperature increases, the flow of viscosity is well controlledand the uniformity and theological characteristic of the PLA materialcan be property maintained. The high volume heated airflow attenuatesthe filaments in a high-output and controlled manner. The spinability isincreased gradually as the maximum draw ratio and natural draw ratio israised, thereby increasing the single fibre tenacity. If the PLA fondantmelt temperature is too high, the PLA material may itself tends todegrade making the screw pressure produced undulate. Consequently, thespinning blowout is not a continuous state and could lead to stretchingthe fibre, making the spinning process difficult and increasing thefuzziness' of the PLA material.

For the production process of PLA, in order to improve the spinability,the primary fiber does not need to have a high crystallinity, otherwisein the drafting process it is very easy to break, which reduces theproduct's intensity in the process of melt-spurt spinning. Thecrystallinity in general before drafting is about 40%, in the bestconditions of cooling temperature and time (cooling temperature is 20°C.), and guarantee that the highest airflow velocity is 5000 m/min,realizing the best melt-spinning spinability.

In the process of crystallization drying, the crystallizationtemperature and the drying temperature are controlled between around110-120° C., extruder temperature from district one to six increasesfrom 170-210° C. and spinning temperature is controlled at 210° C. plusor minus 0.1° C. Drafting speed is 5000 m/min, drafting pressure is0.46˜0.6 MPa, cycloid rate is around 50 H and the speed of nets machineand hot-rolled machine is 17 m/min.

Cooling and Retraction

When cooling the undrawn filament yarns (UDY) from the spinning plate,the cooling speed should be controlled. If the cooling is not managed,the crystalline nature of the stretched undrawn filament yarns can notbe controlled properly and can be difficult to retain for longer timeperiod.

After the cooling of PLA undrawn filament yarns, the undrawn filamentyarns should pass through the high-speed traction stretch where themolecular chain of PLA silk is re-arranged again, the degree oforientation of fibre molecules is increased, the strength of fibre silkis raised in multiples and the product quality is improved.

Needling Binding to Roll

After the cooling and retraction process, the fibre silk is introducedin the needle machine. The needling depth is selected according to theproduction requirement, a depth too deep could damage the fibre and adepth too shallow will result in not enough binding. In general thedensity of needling is large and the fibre tangle degree and theproduction strength is high. The mixed fibres were processed usingneedle punching and thermal bonding to create PLA nonwoven fabric. ThePLA fibre non-woven material can be chosen according to the customerrequirement of width and roil length.

In further embodiments of the present invention the one or more of thefollowing parameters can also be adopted:

A Conveying capacity: once 2 t/h, Saul Sates tan transportation;Secondary transmission is control sending, conveyance medium: dry air.

B: Dry capacity: 500 Kg/h, way for filling type is continuous spraydrying tower.

C: The spinning mode is melt spinning, through a single screw extruderextrusion melting and measuring mixing (speed 30˜40 turn/min is best),entering wick-type filter, filtered melt passing into the metering pumpand then measuring extrusion (metering pump rotation speed is in18˜≅turn/min for the best) into the silk spray head ventage. From silkspray head outbursts primary fiber goes through quench air cooling windinto moulding (wind speed is 0.6 m/min; temperature is 20˜22° C.), thenenters into the draft tube for drafting (draft speed is 5000 m/min), theair needed for drafting must be dry air to go through air compressor andair dryer (pressure is 0.5 Mpa). The flock silk after drafting thenpreliminarily goes into the net through pendulum silk machine(fluctuating frequencies is 45˜50 Hz, the pendulum deflection is 14degrees) and nets machine (the nets machine is negative pressure suctiontype, namely through air volume of 150000 mcubic meters/hour, using thefrequency adjustable fan of 2000 Pa for sucking the below of netsmachine, making the two tightly adherent in the surface of net unit),adopting the hot-rolled method for molding.

Hence, the non woven biodegradable bag 100 of the present invention thusprovides a solution to the aforementioned problems of the prior art byproviding a non-woven biodegradable bag 100 which is biodegradable andcost-effective to manufacture. Thus, after the biodegradable bag hasbeen used and disposed of, it can biodegrade into carbon dioxide andwater by microorganism in composting condition. The non-woven PLAmaterial complies with international sustainable development demands byhaving the characteristics of a complete natural cycle and biodegradableproduct. Tests conducted have revealed that the present invention isbiodegradable within seven days with earth worm and soil testsconfirming that the biodegraded product is non-toxic to the environment.

PLA (polylactic add) is an ideal raw material for leading-edgesustainable applications since it is derived from the naturalfermentation of corn-based products and represents a renewable resource.PLA also has the ability to form fibers, films or foams and is easilyextruded into a variety of forms that have applicability to uniquemarkets. Depending on the process formulation, PLA can be exploited bycombining it with other natural hydrophilic or hydrophobic materials,making PLA an ideal candidate for developing flexible solutions.

PLA's degradation properties, wherein PLA polymers break down intolactic add or its oligomeric lactide forms that are easily metabolized,provides a green alternative where biodegradability is an importantconsideration.

Furthermore, domestically-sourced PLA resins we equally cost competitivewith petroleum-based resins, providing additional options for customers.

Throughout the specification the aim has been to describe the inventionwithout limiting the invention to any one embodiment or specificcollection of features. Persons skilled in the relevant art may realizevariations from the specific embodiments that will nonetheless fallwithin the scope of the invention.

We claim:
 1. A bag made of a non-woven biodegradable polylactide basedmaterial comprising a body portion having at least one side wall and abottom joined together to define a storage space therebetween and anopening at the top of the body portion, wherein the material containspolylactic acid, polyethylene glycol and a chain extender such that thebag is biodegradable and biodegraded products are non-toxic to theenvironment.
 2. The bag of claim 1, wherein the bag is suitable for useas a shopping bag.
 3. The bag of claim 1, further comprising a pair ofhandles, wherein the pair of handles are attached to a top of the bodyportion at their ends.
 4. The bag of claim 1, further comprising atleast one strap member.
 5. The bag of claim 4, wherein the strap memberis attached at or near the top of the body portion and extends acrossthe opening of the body portion of the bag.
 6. The bag of claim 4, wherethe strap member is permanently secured at a first end to a first sideof the body portion, the body portion having a fastening member toreleasably secure a second end of the strap member to a second opposingside of the body portion.
 7. The bag of claim 1, further comprising apair of apertures provided at or near the top of the body portion forreceiving a prong member therethrough to hold the bag in an open state.8. The bag of claim 1, wherein the biodegradable non-woven materialcomprises one or more of the following polymers: polylactic acid,polyethylene glycol, chain extender Joncryl—ADR
 4370. 9. The bag ofclaim 8, wherein the material composition of the biodegradable non-wovenmaterial is 91-94% polylactic acid, 5-8% polyethylene glycol and 1%chain extender.
 10. The bag of claim 8, wherein the biodegradablenon-woven material has a weight-average molecular weight ratio above160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and awater content ≦0.5%.
 11. A method of manufacturing a bag made of anon-woven biodegradable polylactide based material comprising a bodyportion having at least one side wall and a bottom joined together todefine a storage space therebetween and an opening at the top of thebody portion, wherein the material contains polylactic acid,polyethylene glycol and a chain extender such that the bag isbiodegradable and biodegraded products are non-toxic to the environment,the method comprising the following steps: preparing a biodegradablenon-woven material mixture; drying the material to remove residualmoisture; extruding a polylactide (PLA) slicing; heat melting theextruded PLA slicing; purifying the melted PLA resin; spinning thematerial; cooling and retracting the material; needling the materialonto a roll; and forming the bag from the roll of material.
 12. Themethod of claim 12, wherein the material has a weight-average molecularweight ratio above 160000, a dispersion coefficient ≦1.5, a melt indexbetween 20-30 and a water content ≦0.5%.
 13. The method of claim 12,wherein the material is vacuum dried at 80-90° C. such that a moisturecontent of the PLA slicing is less than 200 PPM.
 14. The method of claim12, wherein the extruded PLA slicing is heat melted using a heat screwextruder.
 15. The method of claim 12, wherein the melted PLA material isfiltered prior to the spinning process using a high viscosity fondantproportional pump to squeeze out the impurities by rotation.